The Cougar is one of the military's largest MRAPs and often stays on larger roads. / Force Protection Industries

by Tom Vanden Brook, USA TODAY

by Tom Vanden Brook, USA TODAY

WASHINGTON -- Massive roadside bombs in Afghanistan have forced the military to retrofit armored trucks with better escape hatches to rescue troops wounded in the explosions, according to documents and interviews with defense officials.

The Pentagon has sought to shift $48 million from its accounts to pay for more than 500 new escape hatches for its Cougar version of the Mine Resistant Ambush Protected (MRAP) vehicles and for upgrades to its other versions of the trucks.

That's because, Pentagon records show, Taliban insurgents have buried bombs weighing more than 2,000 pounds that are capable of flipping over 40,000-pound vehicles. Defense officials have added more harnesses inside MRAPs to keep troops from being tossed around inside the vehicles during an explosion, improved lighting to help them escape and more protection on the outside.

Every month, U.S. troops encounter at least two massive bombs, usually formed from homemade explosives packed into multiple 40-pound cooking-oil jugs, said David Small, a spokesman for the Pentagon's Joint IED Defeat Organization.

"Improvements to make equipment safer for war fighters are prudent," Small said. "While overall Afghanistan trends do not see an increase in IEDs with large net explosive weights, there are areas where such larger attacks have occurred, which could warrant action to modify some MRAPs."

The Pentagon has spent $47 billion on MRAPs to protect troops in Afghanistan and Iraq from IEDs, the No. 1 cause of deaths and wounds to U.S. troops. In Afghanistan, there are about 13,000 MRAPs, the principal truck for the 66,000 troops there.

The Cougar is one of the military's largest MRAPs and often stays on larger roads, while a variant developed specifically for Afghanistan, the M-ATV, performs the bulk of the work on smaller roads and in tougher terrain.

Staying one step ahead of bigger bombs exposes a key advantage the insurgents have in the fight, said Peter Singer, director of the 21st Century Defense Initiative at the Brookings Institution.

"People like to talk about how technology has no role in counterinsurgencies, but here again is a great example of the constant back and forth you face even when fighting against insurgents with minuscule budgets," Singer said. "The key question is how do we break free of the cycle where we are spending multimillion dollars to counter their tens or hundreds of dollar advancements."

The military made some progress against IEDs in 2012. U.S. casualties declined by about 50%, and the overall number of bombs fell from its all-time high in 2012 to 15,222. The average size of the IEDs also fell, according to JIEDDO.

Details about the Pentagon request to shift the money to pay for the "Cougar egress kits" was contained in a December reprogramming request submitted by the Defense Department to Congress.

The Pentagon estimates that MRAPs, with their V-shaped hulls and raised chassis, have saved the lives of at least 2,000 troops in Afghanistan. Troops are 17 times more likely to survive an IED blast riding in an MRAP than in a Humvee, the military's former mainstay on the battlefield. Former Defense secretary Robert Gates said an April 2007 report in USA TODAY led to him making the MRAP one of the top priorities of his tenure.